1. Technical Field
The present invention relates to a photoelectric conversion element and a method of manufacturing the same.
2. Related Art
In the related art, it is known that it is possible to obtain a current (a photoelectric current) due to excitation of electrons (an internal photoelectric effect) when light is irradiated onto a semiconductor layer where a plurality of semiconductors with different carrier types are bonded. As elements which use this effect, there are photoelectric conversion elements, which are widely used in photovoltaics including solar power generation, optical sensing systems which use optical detectors, and the like. As representative examples of photoelectric conversion elements, there are pn junction photodiodes which bond a p-type semiconductor and an n-type semiconductor, and these are used as solar panels which use silicon (Si) substrates as the n-type semiconductor, optical detectors in CMOS image sensors which are a type of MOS structure semiconductor, and the like.
There are times when a reverse bias is applied in such photoelectric conversion elements in order to improve responsiveness with respect to the illuminance of light. Due to this, capacitance is reduced by a depletion layer, which is formed in the vicinity of the pn junction, expanding and electrical output with high linearity is obtained with respect to the illuminance of light; however, it is known that it is easy for a current (a dark current), which leaks under conditions where light is not irradiated, to increase under the operation conditions of reverse bias. In such a case, since noise which is caused by the dark current is generated and the lower limit of the minimum value of the output signal is within the noise, the range of the detection values which are able to be distinguished is narrowed and efficient photoelectric conversion is difficult.
In order to suppress the dark current, there is proposed a back-illuminated type solid-state imaging apparatus which has a wiring layer which is formed on a semiconductor substrate and a light receiving section which photoelectrically converts incident light from the opposite side to the wiring layer, where a spontaneous polarization film formed of a material which polarizes spontaneously is formed on a light receiving surface of the light receiving section formed of a pn junction photodiode or the like (for example, refer to JP-A-2011-100845). In this apparatus, it is possible to suppress noise current by polarizing the spontaneous polarization film and forming a hole accumulation layer where positive holes are induced in the light receiving surface side.
However, in JP-A-2011-100845, the light receiving section is merely a typical electron element which has a photoelectric conversion function and does not have any special characteristics. Then, since the configuration where a spontaneous polarization film is provided on the light receiving section or a series of processes are necessary, it is difficult to achieve diversification and it is difficult to use the apparatus in a wide range of applications.